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Figure 2 Pancreatic nerves display differential interactions with islet cell types.
(A) 100 hpf Tg(ins:mCardinal), Tg(sst2:RFP), and Tg(gcga:GFP) zebrafish immuno-stained for acetylated Tubulin (nerves). (B) Segmentation and classification of islet nerves that are in contact with beta, delta, or alpha cell surfaces (magenta). All remaining islet nerves are colored in cyan. (C) Percentage of islet nerve density in contact with the specified pancreatic islet cell type; a majority of the nerves are in contact with beta and delta cells; mean ± standard error of the mean (SEM), n = 7–18 animals, p values from one-way analysis of variance (ANOVA) with Holm–Sidak’s multiple comparisons test; see Figure 2—source data 1. (D) Following exposure to elevated glucose and calcium imaging of pancreatic islet cells and peri-islet neurons at 105–110 hpf, correlation analysis was used to identify beta, delta, and alpha cells with neural activity connection. The percentage of cells of a given type with neural activity connection shows no significant difference between the different cell types; mean ± SEM, n = 6 animals, p values from one-way ANOVA with Holm–Sidak’s multiple comparisons test; see Figure 2—source data 2. (E) Correlation maps of a peri-islet neuron and beta, delta, and alpha cells. Individual cells are plotted with their coordinates. The strength of the correlation (Ravg) between cell pairs is drawn with a grayscale line and the number of connections for each cell is represented by the circle size. (F) Normalized calcium traces of pancreatic islet cells (including delta, beta, alpha, and unidentified cells) and a neuron (n). Individual islet cells were assigned to a cell type and given a cell id. (G) Correlation matrix of cell activity. Individual cells were assigned to a cell type (including delta, beta, alpha, and unidentified cells, and neurons) and average correlation coefficients for given cell pairs (matrix row-column intersects) were calculated. Areas displaying homotypic interactions are highlighted. (H) Average correlation coefficients from individual animals between homotypic cell pairs were divided into two groups (cells with or without neural connection); n = 6 animals, p values from paired t-tests.